Magnetically controllable semiconducting resistance device and method of its manufacture



Dec, 1, 1959 I o. HALLA ET AL 2,9159584 MAGNETICALLY CONTROLLABLESEMICONDUCTING RESISTANCE DEVICE AND METHOD OF ITS MANUFACTURE FiledJune 28, 1955 3 Sheets-Sheet 1 Fig.4 Fig.9

Dec. 1, 1959 o HALLA ETAL 2,915,684

MAGNETICALLY CONTRdLLABLE SEMICONDUCTING RESISTANCE DEVICE AND METHOD OFITS MANUFACTURE Filed June 28. 1955 3 Sheets-Sheet 2 I I 1 2 HM:

Dec. 1, 1959 o. HALLA ETAL 2,915,684

MAGNETICALLY CONTROLLABLE SEMICONDUCTING RESISTANCE DEVICE AND METHOD OFITS MANUFACTURE Filed June 28, 1955 3 Sheets-Sheet 3 I I l l 600 800I000 I200 s FIGJ I United States Patent MAGNETICALLY CONTROLLABLESEMICON- DUCTING RESISTANCE DEVICE AND METH- OD OF ITS MANUFACTUREOttkar Halla and-Friedrich Kuhrt, Nurnberg, Germany,

assignors to siamens-s'chuckertwerke Aktiengesellschaft, Berlin,Germany, a corporation'of Germany ticularaspect, to voltage generatingvsemiconductor devices of the kind known as Hall-voltage generators,

v Patented Dec. 1,. 1959 i their preparation and use in the laboratory.In the first It'has been proposed to utilize the magneticallyresponsiv'e change in resistance, observed in certain resistor bodies,as a means for measuring magnetic fields, for magnetically measuringelectric currents or other currentdependent magnitudes and also forvarious other purposes, such as the computation of mathematicalproducts, the electric representation of speeds of revolution, or themodulation of a carrier wave. These proposals particularly contemplateusing for such purposes a resistor body formed of the recentlydiscovered semiconducting compounds having' an especially. high carriermobility, i.e., a mobility of about60'00 c'mF/volt second or more, andpreferably above 10,000 cm. /volt second. These compounds comprise thebinary compounds of one of. the elements aluminum, gallium, indium inthe third group, subgroup B, of the periodic system with one of'theelements phosphorus, arsenic, antimony in the fifth group, subgroup B,of the periodic system of elements. These and othersemiconducting'cornpounds of this type, briefly The semiconductorcompounds of a carrier mobility above 6,000 cmf /volt second representsubstances of unique electrical behaviour. Above all, their electricresistance exhibits a particularly pronounced. dependency upon changesin an exteriorly applied magnetic field; the

Hall voltage and the Hall constant are particularly high- The Hallconstant is a property inherent in the substance and is the basis forthe so-called Hall effect. This effect has long been known. It was firstobserved with metals, particularly bismuth, and consists inthephenomenon that a current-traversed resistance body, usually shaped as awafer, exhibits a displacement of its lines of equipotential points whenexposed'to a magnetic field having a field corn-ponent transverse to thedirection of current flow. As a result of the displacement, two mutuallyspaced points; previously at the same potential, new are atrespec-tively different potentials, thus providing the so-called Hallvoltage which can be tapped-0E from two Hall electrodes mounted ontheresistor body. The significance of the-novel semiconductor compounds,relative to the Hall effect, resides in that they have made it possiblefor the first time to generate a Hall-voltage power output of suchalarge magnitude as to permit the direct application of .the Hallvoltage for the operation of ordinary moving-coil instruments as well asfor the direct control of electromagnetic relays, magnetic amplifiersand other power consuming devices.

As'heretofore known and disclosed, however, the magneticallycontrollable resistance devices and Hall generators leave much to bedesired in respect to their manufacture and usein general practice,'- ascompared with i place, the resistance body of such devices, particularlyif made of high-mobility semiconductor compounds, formed as a thin plateor water, is apt to be fragile, especially if the particular crystallinesubstance employed is brittle. Particularly sensitive are the placeswhere the electrodes or electric leads are attached to the body. Thereis also the danger that trouble or inaccurate performance may occur, dueto thermo-responsive stresses caused by nonuniform heating of theresistance body when traversed by current. It has been difiicult, therefore, to produce these devices with such a slight thickness of theresistance wafer as would be best suited for the desired electrical:operation, nor could such a thinwafer device reliably be used in actualpractice or under rugged operating conditions.

It is an object of our invention to obviate the abovementionedshortcomings and to devise a manufacturing method and Ya product thatpermits the making of the resistance body of the magnetically responsiveresistance device as thin as is desirable for bestelectrical-performance, without entailing excessive difficulties inattaching the electrodes and leads during manufacture, and with outrendering the device sensitive to damage or electrical trouble when inuse. Indeed, it is another object of our invention to improve suchdevices in respect to their qualities in technical and practical use sothat they can be-reliably handled and are well suited for ruggedoperating conditions. It is also an object of our invention tofacilitate mounting the resistance device and to provide a rigid andsecure positioning of the electric leads so that, once the device hasbeen balanced or calibrated for the com pensation of inductivecomponents due to variable magnetic fields, such a compensation cannotbe disturbed by subsequent mounting or use of the device. Our inventionfurther aims at providing the device with a hermetic seal againsthumidity and other mechanical or chemical corrosive attacks from theoutside. Another object is to achieve maximum safety from trouble due totension caused by non-uniform heating of the resistance body.

To achieve these objects, and in accordance with our invention, we embedthe resistance body of a device of the above-mentioned type in a cast ormolded body of a hardening or hardenable electric insulatingmateriaLpreferably in a casting of synthetic resinous plastic, and wealso include within the insulating material the leads and terminals orHall electrodes connected-with the resistance body. The hardened andrigid insulating enclosure is given two surfaces parallel to the broadsides of the embedded wafer. The surfaces are to be traversed by themagnetic flux to which the wafer is to be subjected; for instance, theymay be engaged in face-to-face contact with the pole faces of a magneticfield structure. Ac: cording to another feature of the invention, theenibedded current supply or voltage-output leads are so arranged thatnone of them extends above one or both of the broad-side surfaces of theresistance body; and after the embedding material has hardened, thesurface or surfaces of the resistance body are subjectedtomaterial-removing processing by any mechanical, chemical,electro-chemical or other method suitable for reducing the thickness ofthe embedded resistance body.

We are aware of the fact that transistors, that is semiconductor bodieshaving rectifying properties, have been embedded in plastic material forprotection. In contrast thereto, our invention not only affordsprotection of the magnetically controllable resistance body but, byvirtue of the other features mentioned in this specification, alsoresults in considerable improvements in electrical qualities, mainly dueto the fact that the embedded resistance bodies can be reduced to athickness of a much smaller magnitude than heretofore attainable.

In resistance devices that are to vary their ohmic resistance independence upon the magnetic field, the invention readily affords givingthe resistance a high ohmic magnitude far beyond those heretoforeattainable. This is an important advantage for impedance matchingpurposes. Furthermore, despite the reduced thickness of the resistancebody, its current-carrying capacity is considerably increased incomparison with a non-embedded body, this being due to the fact that theembedding material improves the dissipation of heat from the resistancebody.

In addition, Hall-voltage generators according to the invention withembedded resistance bodies of semiconducting compounds of high carriermobility, exhibit the particularly salient advantage of being operablewithin a greatly increased control range.

How these objects and advantages come about will presently be explainedmore in detail.

The Hall voltage U is determined by the following equation:

Bdl

In this equation, R denotes the Hall constant, a the thickness of thesemiconducting resistance body across which the Hall voltage isgenerated, B the magnetic induction applied to the semiconductingresistance body, and I the control current flowing through the body.Normally, the magnitudes B and I represent the variable controlmagnitudes of the Hall generator. For any given Hall generator themaximum value of the Hall voltage UHmax is attained when H and I assumetheir maximum values. The maximum magnetic induction readily obtainablewith the aid of the usual magnet and the like technical means is in theorder of B l0,0OO Gauss. The control current i is more or less limitedby the heat dissipation occurring during the heating of the Hallgenerator. The thickness d of the resistance body represents a thirdvariable in the Equation 1 for the Hall voltage U However, as regardsthe de endency of the attainable maximum Hall voltage U upon thethickness d, it must be taken into account that the permissible maximumof control current Ismax is a function of the thickness d. That is, itfollows from the energy balance for a Hall generator whose resistancebody has a width b, an electric conductance and an effective heattransfer number It, that for a given permissible heating of themagnitude AT the maximum current I must satisfy the equation max Itfollows from Equations 1 and 2 that the maximum of attainable Hallvoltage corresponds to UH....=R-B....-b /2a'rm.. (3)

consequently, the maximum Hall voltage increases with an increasing heattransfer number h and with a decreasing thickness d of the resistancebody.

In view of these conditions the advantages afforded by the inventionbecome more clearly apparent if one considers that with a semiconductingresistance body not embedded in bracing material a reduction of thethickness d is possible only down to a certain limit. However, if theresistance body, according to the invention, is embedded in a protectivebody, it is not only possible to go considerably below theabove-mentioned limit down to thickness values d much smaller than thoseheretofore applicable, but the heat transfer number it is simultaneouslyincreased to a substantial extent so that in the foregoing Equation 3for U the quotient d is favorably modified in two respects, namely byreducing l its denominator and simultaneously increasing its numerator.

The method described in the following has been found particularlyfavorable for embedding the resistance body. The plateor wafer-shapedresistance body is first produced with such a sufiicient thickness thatthe required current supply terminals and Hall electrodes, includingtheir respective connecting leads, can be attached without difficulty,for instance by soldering and that, when making the desired connectionsand applying any desired inductive balancing or calibrating operation,there will be no danger of damage to the resistance body. It ispreferable to embed the semiconducting resistance body with itselectrodes and leads in a casting of resinous plastic. For this purposea hardening or hardenable synthetic resin is preferably employed inwhich the hardening is due to polymerization. Suitable substances ofthis kind, for instance, are ethoxylin and polyester resins. A preparedresistance body with current-supply terminals, Hall electrodes andconnecting leads is placed into a suitable mold, and the castable resinis poured into the mold in liquid condition. Subsequently, care is takenfor polymerization or hardening of the resinous casting in the knownmanner and in accordance with the manufacturers requirements for theparticular resin used. However, other embedding methods are likewiseapplicable, for instance embedding of the resistor assembly into asynthetic resin powder which is subsequently liquified by heat treatmentand permitted to polymerize or harden.

After the semiconducting plate or wafer of comparatively large thicknessis embedded in an insulating body according to any of the methodsdescribed, and after the insulating body is hardened, the semiconductorwafer is subjected to a thickness reducing operation by chemical ormechanical removal of material until the semicom ductor body has theultimately desired thickness.

An example of the above-described method according to our invention isthe following. A Hall plate is prepared from monocrystalline indiumantimonide (or indium arsenide) with a length of 8 to 15 mm., a width of3 to 8 mm. and a thickness of about 1 mm. The Hall electrodes andcurrent leads are soldered to the plate, this being readily possiblebecause of the relatively large thickness of the plate. The plate,electrodes and leads are then embedded as described above in a castingof polyester resin so as to form an assembly of the design describedbelow with reference to the drawings. After hardening of the enclosure,one side of the enclosure and of the embedded body is ground down to thedesired thickness such as 0.1 to 0.5 mm.

According to another feature of the invention the embedding mass forproducing the protective body comprises or consists of ferrite materialor a similar electrically non-conducting, magnetizable material of highpermeability. According to a modification of this type, ferrite powderis used as a component of a mixture by adding it to a pourable resin orsimilar synthetic material. The use of such electrically insulating butmagnetically conducting materials permits giving the protective body alarger thickness than otherwise applicable, because the portions of theprotective body located between the magnet poles and the resistance bodynow have a greater magnetic conductivity and hence no longer act like anair gap. Conversely, for a given thickness of the protective body thereduced magnetic resistance results in a correspondingly higherinduction to be effective within the resistance body proper. However,when thus applying a magnetically conducting material care should betaken that this material covers only those surfaces of the resistancebody that extend trans verse or perpendicular to the direction of themagnetic field acting upon the resistance body, thus preventing theoccurrence of detrimental magnetic bridges or shortcircuits laterallyaround the resistance body from one to'the opposite pole of the magneticfield structure.

For further describing the invention and for explaining the advantagesachieved thereby, reference is made in the following to the drawings inwhich:

Fig. 1 shows a Hall-voltage generator according to the invention, Fig. 2is a sectional side view of the same device and includes a showing ofthe appertaining magnetic field system, Fig. 3 is a top view of thedevice exclusive of the field system, and Fig. 4 is a cross sectionalong the line IVIV.

Figs. 5 and 6 are explanatory of a manufacturing method according to theinvention and show, in cross section, the same Hall-generator device intwo stages of manufacture respectively.

Fig. 7 is a cross-sectional view of another Hall-generator deviceaccording to the invention.

Fig. 8 is a top view of still another embodiment, and Fig. 9 shows across section along the line IX-IX in Fig. 8.

Fig. 10 is a cross section of a further embodiment according to theinvention.

Figs. 11 and 12 are coordinate diagrams explanatory of the operation ofHall-voltage generators according to the invention.

The same reference characters are used in the various illustrations fordenoting functionally similar elements respectively. For lucidillustration it is assumed that the insulating enclosure in theillustrated embodiments is formed of transparent material, although thisis not an indispensable requirement of the invention.

The embodiment illustrated inFigs. 1 to 4 is suitable for a largevariety of applications. The device comprises a protective body ofresinous plastic in which a wafer-shaped resistance body 2 is embedded.The resistance body 2 consists of one of the above-mentionedsemiconducting materials, for instance of a monocrystalline body ofindium arsenide and may be given the above-mentioned dimensions.

The protective resinous body may be looked upon as comprising twoportions merging with each other, namely a portion 1 containing theresistance body 2, and a portion 3 that accommodates the electricterminals and serves as a mechanical support or mounting base.

The thickness of portion 1 of the protective body need not be largerthan required for securely mounting the resistance body 2 with theterminals, electrodes and electric leads. For instance, we prefer makingthe portion 1 of protective body not thicker than about 1 mm. at thelocation where the resistance body 2 is embedded.

The resistance body 2 has two lineor area-shaped current supplyterminals 4, 5 which are simply formed by the connecting leads 6, 7themselves. The resistance body 2 is further equipped with twopoint-shaped Hall electrodes 8, 9 connected to respective leads 10 and11. The Hall electrodes are located opposite each other in a directiontransverse to that of the current flowing between the terminals 4 and 5.The two connecting leads 10 and lill are twisted about each other andare connected with respective terminal lugs 12 and 13 located one abovethe other for attachment of respective wires by soldering. The currentsupply leads 6, 7 extend separately through the insulating protectivebody and are connected with two soldering lugs 14 and 15 respectively.The lugs 12 to 15, which may be substituted by any other terminalelements, are only partially embedded in the portion 3 of the protective body, so that the terminal ends project out of that body. Twobores 16 and 17 in portion 3 of the protective body permit mounting thisbody on a suitable support.

According to Figs. 1 and 2, the portion ll of plastic material isinserted between the poles P and P or a magnet structure M. To this end,the portion 1 has two planar, preferably ground surfaces, in closecontact with the respective pole faces. The field of the magnetstructure is produced or controlled by a winding W. The field extendsthrough the semiconductor bodyj2 perpendicwlarly to the direction of thecurrent flow between the terminals 4, 5 and also perpendicularly to theaxis defined by the Hall point-electrodes 8 and 9. When the magneticfield strength is zero and the semiconducting resistance body 2 istraversed by current supplied through the terminals 14 and 15, then thepoint electrodes 8 and 9 have the same potential, that is, the voltagedifference between them is zero. When the magnetic field has a finitevalue, due to proper excitation of winding .W, then the two Hallelectrodes 8 and 9 assume different potentials so that a Hall voltage isgenerated between them. The polarity and magnitude of the Hall voltagedepends upon the polarities and magnitudes of the magnetic field and ofthe current, and hence can be varied by varying either or both of thecontrolling field and current parameters.

In the manufacture of devices according to the invention, it isimportant to take care that the embedded connecting leads of theresistance body are so arranged within the protective body that they donot pass over both of the resistance body surfaces that extendtransverse or perpendicular to the direction of the magnetic controlfield to be applied. Preferably also the embedded connecting leads areso laid out that they do not pass across the plane or planes of thejust-mentioned surfaces. In this manner, at least one surface of theresistance body remains freely accessible for subsequent diminution inthickness of the resistance body. As mentioned, such reduction inthickness, requiring the removal of material from the resistance body,can be effected by any suitable method, for instance by mechanicalmachining or chemically. We prefer to remove the material by grinding.In view of such a subsequent reduction, the embedding method can be soconducted that the portion or surface of the resistance body from whichmaterial is to be subsequently removed is not covered by the embeddingmass of material. For example, the surface of the resistance body may beleft projecting out of the embedding material or it may be placed flushwith a neighboring surface of the protecting body.

In some cases, the subsequent removal of material from the resistancebody may have the effect of releasing inherent mechanical tensions, andthis may damage or destroy the resistance body. Such occurrences,however, can be avoided by employing suitable expedients to prevent suchmechanical 1 tensions. ance body may be subjected to normalizingtreatment by applying elevated temperature, similar to the heating orannealing generally applied to castings for the same purpose ofeliminating interior tension. Good results have been obtained by slowlycooling the resistance body from the hardening temperature down to thenormal use temperature of the resistance body. However, we generallyprefer making certain from the outset that interior mechanical tensionsdo not occur. This canbe achieved, for instance, by employing syntheticresins of corresponding properties. Of course, any such means foreliminating interior tension are not necessary in cases where thesemiconductor substance is not brittle and fragile but has sufiicientelasticity to obviate damage of the kind mentioned.

For preventing destruction or damage of the embedded resistance. bodydue to subsequent removal of material therefrom, the following method,described with reference to Figs. 5 and 6, has also been found ofadvantage in cases where brittle semiconducting materials are involved.When producing the protective enclosure around the resistance body, theenclosure 1 is at first provided with bracing ribs 21 on the sideopposite to the side of the resistance body 2 to be subjected tosubsequent machining' or other removal of material. Upon hardening ofthe enclosure 1, the resistance body 2 is reduced to the desiredthickness, preferably by grinding down to the dashed line 22 in Fig. 5.Thereafter the machined sur-' face of the resistance body is againenclosed bycasting For instance, the resist-- resinous material upon it,so that the newly cast material 23 (in Fig. 6) merges with the rest ofthe protective body. Subsequently, the bracing ribs 21 located on theother side of the protective body are removed, for instance also bygrinding, so that the device has the final cross-sec tional shape shownin Fig. 6. The subsequent covering of the machined surface of theresistance body has also the advantage of securing an increaseddissipation of heat from that surface.

Another way of preventing damage or destruction of the embeddedresistance body due to the release of internal mechanical tensions is toplace the resistance body with the surface not to be machined onto aplastically deformable support so that this plastic support is locatedbetween the resistance body and the surrounding enclosure 3.

Thus, according to Fig. 7, the semiconductor body 2 is placed against aplate or wafer 24 of elastomer material such as rubber or a syntheticelastomer, and the elastic wafer 24 is embedded into the rigid plasticof enclosure 1 together with the body 2. As shown, the elastic plate 24may cover not only the top surface of body 2 but may also reach aroundits narrow sides. After hardening of enclosure 1, the body 2 issubjected to grinding to reduce its thickness down to the dashed line22. During grinding, the elastomer material 24 absorbs shocks thusprotecting the body 2. If desired, the machined and exposed surface ofbody 2 may be subsequently covered as described above.

While in the embodiment according to Figs. 1 to 4 only one surface ofthe resistance body is readily accessible for the subsequent removal ofmaterial, the embodiment shown in Figs. 8 and 9 has both magnetic-fluxtraversed surfaces freely available for reduction in thickness. For thispurpose the lead 10 connected to the Hall electrode 8 is subdivided intotwo branches which are laterally laid about the narrow faces of theresistance body 2 and are thereafter again united to a single lead. Sucha balanced subdivision into two branches need not be used if noappreciable disturbance is to be expected from any component effectoccurring in the circuit of the Hall electrodes due to the applicationof a magnetic field varying with time.

To attain the largest possible heat dissipation from the resistancebody, the embedding is preferably made of a good heat conductingmaterial. The heat conductance of the material can be further increasedby adding to the resinous or other material to be cast or molded anamount of quartz meal or electrically non-conducting substances, forinstance metal oxides.

The heat dissipation by thermal conductance of the enclosing materialand the resulting improvement in properties of the device according tothe invention, however, can also be increased by externally appliedmeans. Thus, according to a modification of the invention, theprotective enclosure is made longer than the embedded resistance bodybeyond the extent required for embedding the body. This is particularlyeffective if the enclosure consists of a material of high thermalconductance. According to another feature serving the same purpose,cooling vanes or similar heat conducting elements are embedded in theenclosure. For obtaining a slight overall thickness of the protectiveenclosure, these heat conducting vanes or other means are made toproject out of the protective body at its narrow sides. The coolingvanes or other heat conducting members may be so designed or arrangedthat they dissipate heat to an adjoining object. Particularly suitablefor dissipating the heat by conductance is the magnetic core of themagnetic field structure used for exciting the resistance body. This isthe reason why it is particularly advantageous to place the surface ofthe protective body directly in intimate face-to-face contact with thepole faces of the magnetic field structure to whose field the resistancebody is to be subjected. In this manner a particularly large heatdissipation by conductance is secured. A particularly effective heatconductance is further attained by inserting, preferably casting, athermal contact mass between the protective body and the pole faces ofthe magnetic field structure.

The Hall generator illustrated in Fig. 10 embodies the modificationsjust described. The semiconducting resistor body 2 of this device isembedded in a rigid enclosure 31 of much greater length than needed forthe embedding proper. The enclosure is formed of polyester resin or asimilar synthetic plastic mixed with quartz meal. Two cooling vanes 25,26 are also embedded and project out of the enclosure 31. The resistorbody 2 has its upper surface flush with the top surface of theenclosure. The lower surface of enclosure 31 is in intimate,heat-conducting contact with the face of pole piece P of the magnet (seeM in Fig. 2). A layer 27 of heat-conducting electrically insulatingmaterial is cast into the space between the body 2 and the face of polepiece P Layer 27 may consist of a mixture of ferrite powder with asynthetic plastic to secure not only a good heat transfer from body 2 topole piece P but also a good magnetic connection.

The considerable improvement achieved by virtue of the invention will bemore fully understood from the graphs presented in Figs. 11 and 12.

Fig. ll indicates the measured temperature increase AT of a resistancebody formed of indium arsenide versus the controlling current I flowingthrough the body. The temperature curves were obtained with a length andwidth in the order of magnitude of a few millimeters, and a thickness inthe order of magnitude of a few one-tenths of a millimeter. The curvesshown on the diagram, in harmony with the above presented equations,follow the square-law dependency expressed by:

I =2b .h.d.AT 4

Curve I applies to the resistance body when not embedded but operatingin air. Curve II applies to the specimen embedded in a protective bodyof a cast resin operating in air. Curve III applies to a specimenembedded in a cast body of resin operated in intimate face-to-facecontact with the pole faces of the appertaining magnetic fieldstructure. As can be seen from a comparison of the three curves, theheat transfer number in case 11 is about 2.5 times as large, and in caseIII about 15 times as large as the heat transfer number of theunenclosed resistance body in air.

The resulting improvement of the Hall-generator operation is apparentfrom the diagram of Fig. 12 which is based upon a resistance body ofsubstantially the same dimensions as mentioned above with reference toFig. 11. Fig. 12 indicates the dependency of the Hall voltage U upon thecontrol current I a constant magnetic field being applied to theresistance body. The straight lines entered into the diagram applyrespectively to the values of thickness of tl e resistance bodyindicated in millimeters next to the respective lines. The hyperboliccurves I, II and III represent the limit curves up to which theresistance body can be controlled without detriment to its desiredproperties. As in Fig. 11, curve I in Fig. 12 applies to thenon-embedded resistance body, curve II to the embedded resistance body,and curve III to the embedded resistance body in intimate contact withthe two pole shoes of the appertaining magnetic field structure.

The curves I to III are based upon a given permissible maximum increasein temperature. The curves manifest a considerable widening of thecontrol range of the Hall generator as well as an increase in Hallvoltage, this voltage increase being due to the fact that the embeddingof the resistance body permitted grinding its thickness down to that ofa thin wafer. The increase in Hall voltage is particularly apparent froma study of the two linear characteristics shown by heavy lines. Thelower straight line represents the relation between the Hall voltage Uand the control current I as well as the utilizable control range forthe non-embedded resistance body used in the manner heretofore known,whereas the upper straight line applies to a specimen embedded in aprotective body according to the invention and ground down to athickness of 0.1 mm.

Another advantage afforded by the reduction in thickness of theresistance body is the increase in the interior resistance R, effectivewithin the circuit of the Hall electrodes. This is important for manyapplications where impedance matching or similar adaptations are desiredor necessary. For instance, if the Hall generator is to be used for thecontrol of a magnetic amplifier it is much easier to design a magneticamplifier having an input circuit matched to a resistance ofapproximately ohms rather than to a resistance of only about 1 ohm orless.

As can be shown in calculation, the maximum attainable power output inthe Hall-voltage generating circuit of a semiconducting resistance bodyis proportional to the effective heat transfer number It. In the abovementioned examples, therefore, the further advantage of increasing thepower output by the factor 2.5 and respectively is achieved.

Relative to the data mentioned with reference to Figs. 11 and 12 it maybe added that these data by no means represent highest attainablevalues. By application of the further, above-mentioned improvements, forinstance by the use of a resinous casting admixed with quartz meal orthe like, a further increase in the desired properties is obtained. Asabove mentioned, the data apparentfrom Figs. 11 and 12 apply to aresistance body of given dimensions and consist of a givensemiconducting compound, namely, indium arsenide, having a Hall constantR in the order of magnitude of about 120 cm./ amp. sec. Similar and inpart better results are obtainable with resistance bodies of differentsemi-conducting compounds.

The term high carrier mobility, as employed herein, means a mobility ofat least about 6000 cm. volt second.

While we have shown and described particular embodiments of ourinvention, it will occur to those skilled in the art that variouschanges and modifications may be made without departing from theinvention. We therefore aim in the appended claims to cover all suchchanges and modifications as fall within the true spirit and scope ofour invention.

We claim:

1. A Hall effect resistance device for controlling electric current flowas a function of magnetic field strength, comprising a plate-shapedsemiconductor member comprised of a binary compound of high carriermobility, current supply and Hall voltage electric conductor meansjoined with said member, and an electrically insulating and supportingstructure comprising a first portion within which said member and saidconductor means are embedded, and which is only slightly greater inthickness than the thickness of said member, and a second portionintegral with said first portion and of substantially greater thicknessthan the thickness of said first portion, said second portion compriingmeans for mounting said supporting structure and for electricalconnection to said conductor means. I

2. A Hall effect resistance device for controlling electric current flowas a function of magnetic field strength, comprising a plate-shapedsemiconductor member having opposed wide area surfaces and comprised ofa binary compound of high carrier mobility, electric conductor meansjoined with said member, a substantially rigid, heat conductiveelectrically insulating covering of plastic in which said member andsaid conductor means are embedded, said embedded conductor meanscomprising a first pair of wires for deriving Hall voltage fromsaidmember and a pair of wires for passing current through said member,one conductor of said first pair beingdivided into two parts whichsurround the periphery of said member and join together again as'asingle conductor.

3. A Hall effect resistance device for controlling electric current flowas a function of magnetic field strength,

comprising a plate-shaped "semiconductor member comprised of a binarycompound of high carrier mobility, current supply and Hall voltageelectric conductor means joined with said member, a substantially rigid,electrically insulating covering of plastic in which said member andsaid conductor means are embedded, and terminal connector means joinedwith said electric conductor means and having connector lug elementsprojecting from said insulating covering, said insulating covering beingprovided with a material imparting high thermal conductvity.

4. A Hall effect resistance device for controlling electric current flowas a function of magnetic field strength, comprising a. plate-shapedsemiconductor member comprised of a binary compound of high carriermobility, current supply and Hall voltage electric conductor meansjoined with said member, a substantially rigid, electrically insulatingcovering of plastic in which said member and said conductor means areembedded, and terminal connector means joined with said electricconductor means and having connector elements projecting from saidinsulating covering, said insulating covering being provided withheat-radiating fins embedded in and projecting from the narrow edges ofsaid covering.

5. A Hall effect resistance device for controlling electric current flowas a function of magnetic field strength, comprising a plate-shapedsemiconductor member comprised of a binary compound of high carriermobility, current supply and Hall voltage electric conductor meansjoined with said member, a substantially rigid, heat conductiveelectrically-insulating covering comprising plastic in which said memberand said conductor means are embedded, terminal connector means joinedwith said electric conductor means and having connector elementsprojecting from said insulating covering, and an electromagnet havingopposed pole shoes and being disposed with respect to said embeddedmember so as to pass a magnetic field perpendicular to the planarsurfaces thereof, wherein at least one of the covering surfaces isparallel to one of the major planar surfaces of said member and is indirect contact with one of said pole shoes, whereby a high rate ofconductive heat dissipation to said electromagnet is effected.

6. A Hall effect resistance device for controlling electric current flowas a function of magnetic field strength, comprising a plate-shapedsemiconductor member comprised of a binary compound of high carriermobility, current supply and Hall voltage electric conductor meansjoined with said member, a substantially rigid, electrically-insulatingcovering comprising plastic in which said member and said conductormeans are partly embedded, one of themajor planar surfaces of the memberbeing exposed, terminal connector means joined with said electricconductor means and having connector elements projecting from saidinsulating covering, and an electromagnet having opposed pole shoes andbeing disposed with respect to said embedded member so as to pass amagnetic field perpendicular to the planar surfaces thereof, wherein thecovering surface of plastic is parallel to one of the major planarsurfaces of said member, a thermally conductive electrically insulatingplastic mass disposed between said exposed surface and its respectivepole shoe for dissipating heat to said electro-magnet through said mass.

7. The method of producing a Hall effect electric resistance device ofmagnetically responsive resistance, which comprises joining currentsupply and Hall voltage electric conductor means with a fiat resistancebody of a semiconducting compound of high carrier mobility and arrangingsaid conductor means so that at least one wide area surface of said bodyis left unobstructed, molding ilil an electrically insulating andhardenable plastic material about said body and said means whereby, uponhardening of said material, said body and said means are rigidlyembedded in said material, and removing substance from said unobstructedsurface of said body to reduce the thickness of said body.

8. The method of producing a Hall effect device for controlling electriccurrent flow as a function of magnetic field strength, which comprisesconnecting current supply and Hall voltage electrical conductors with aHall plate comprised of a binary compound of high carrier mobility,arranging said conductors so that at least one Hall surface of saidplate remains unobstructed, molding an electrically nonconductive andhardenable material of plastic about said plate and said conductors,cutting away layers of said hardenable material after hardening togetherwith layers of said one of said Hall surfaces to reduce the thickness ofsaid Hall plate, and finally covering said cut-away Hall surface withresinous material.

9. The method of producing a Hall effect device for controlling electriccurrent flow as a function of magnetic field strength, which comprisesconnecting current supply and Hall voltage electrical conductors with aHall plate comprised of a semiconductor of high carrier mobility,arranging said conductors so that at least one Hall surface of saidplate remains unobstructed, molding an electrically nonconductive andhardenable supporting mem ber of plastic about said plate and saidconductors, said supporting member being molded with strengthening ribsat the side of one of the Hall surfaces of said Hall plate, cutting awaylayers of said hardenable material after hardening together with layersof the other of said Hall surfaces to reduce the thickness of said Hallplate, covering said cut-away Hall surface with a resinous material, andfinally cutting away said molded strengthening ribs to reduce saidcovering structure at said first-mentioned Hall surface.

10. The method of producing a Hall effect device for controllingelectric current flow as a function of magnetic field strength whichcomprises connecting electrical conductors with a Hall plate comprisedof a binary compound of high carrier mobility, arranging said conductorsso that at least one Hall surface of said plate remains unobstructed,embedding one Hall surface and the peripheral edges of said Hall platein a layer of electrically non-conductive resilient material, molding anelectrically nonconductive and hardenable material of plastic about saidresilient material and said conductors, and finally cutting away saidhardenable material together with layers of the other of said Hallsurfaces to reduce the thickness of said Hall plate.

ll. A Hall-effect apparatus comprising a semiconductor plate havingopposite wide area faces and a perimetric area, protective support meansfor the plate comprising an electrically insulating hardened plasticmaterial embedding at least one of said faces, the thickness of theplastic thereon being not more than one mm., and also encasing aperimetric area of the plate, means comprising magnet poles for imposingmagnetic flux across said wide area faces, the plate being locatedbetween the poles, at least one of said poles being in direct heatexchange with said hardened plastic material on one of said faces,electrical insulating means interposed between the other pole and theother of said faces, said plate having Hail voltage terminals andcurrent supply terminals, leads connected to said terminals, the leadsbeing in part embedded in said hardened plastic material and in partextended outwardly therefrom.

12. A Hall-effect apparatus comprising a semiconductor plate havingopposite wide area faces and a perimetric area, protective support meansfor the plate comprising an electrically insulating hardened plasticmaterial embedding at least one of said faces, the thickness of theplastic thereon being not more than one mm., and also encasing aperimetric area of the plate, means comprising magnet poles for imposingmagnetic flux across said wide area faces, the plate being locatedbetween the poles, at least one of said poles being in direct heatexchange with said hardened plastic material on one of said faces,electrical insulating means interposed between the other pole and theother of said faces, said plate having Hall voltage terminals andcurrent supply terminals, leads connected to said terminals, the leadsbeing in part embedded in said hardened plastic material and in partextending outwardly therefrom, the embedded part of the leads connectedto the Hall terminals being brought together and entwined about eachother.

13. A Hall-effect apparatus comprising a semi-conductor plate havingopposite wide area faces and a perimetric area, protective support meansfor the plate comprising an electrically insulating hardened plasticmaterial embedding at least one of said faces, the thickness of theplastic thereon being not more than one mm., and also encasing aperimetric area of the plate, an elastomer sheet interposed between thehardened plastic sheet and the said one face, means comprising magnetpoles for imposing magnetic flux across said wide area faces, the platebeing located between the poles, at least one of said poles being indirect heat exchange with said hardened plastic material on one of saidfaces, electrical insulating means interposed between the other pole andthe other of said faces, said plate having Hall voltage terminals andcurrent supply terminals, leads connected to said terminals, the leadsbeing in part embedded in said hardened plastic material and in partextended outwardly therefrom.

14. A Hall-effect apparatus comprising a semi-conductor plate havingopposite wide area faces and a perimetric surface area, protectivesupport means for the plate comprising an electrically insulatingheat-conducting hardened plastic material embedding all of said plate,means comprising magnet poles for imposing magnetic flux across saidwide area faces, said poles being in direct contact with said hardenedplastic material on said faces, said plate having Hall voltage terminalsand current supply terminals, leads connected to said terminals, theleads being in part embedded in said hardened plastic material and inpart extended outwardly therefrom.

15. A Hall-effect apparatus comprising a semi-conductor plate havingopposite wide area faces and a perimetric surface area, protectivesupport means for the plate comprising an electrically insulatingheat-conducting hardened plastic material embedding all of said plate,means comprising magnet poles for imposing magnetic flux across saidwide area faces, said poles being in direct contact with said hardenedplastic material on said faces, said plate having Hall voltage terminalsand current supply terminals, leads connected to said terminals, theleads being in part embedded in said hardened plastic material and inpart extended outwardly therefrom, said plastic material having embeddedtherein a heat conductance increasing powder.

16. A Hall-effect apparatus comprising a semi-conductor plate havingopposite wide area faces and a perimetric surface area, protectivesupport means for the plate comprising an electrically insulatingheat-conducting hardened plastic material embedding all of said plate,means comprising magnet poles for imposing magnetic flux across saidwide area faces, said poles being in direct contact with said hardenedplastic material on said faces, said plate having Hall voltage terminalsand current supply terminals, leads connected to said terminals, theleads being in part embedded in said hardened plastic material and inpart extended outwardly therefrom, said plastic material having anadmixture of a magnetic ferrite to increase the heat conductivity andthe magnetic induction.

17. A Hall-effect apparatus comprising a semi-conductor plate havingopposite wide area faces and a perimetric area, protective support meansfor the plate comprising an electrically. insulating heat conductinghardened plastic material embedding at least one of said faces, thethickness of the platic thereon being not more than one mm., and alsoencasing a perimetric area of the plate, means comprising magnet polesfor imposing magnetic flux across said wide area faces, the plate beinglocated between the poles, at least one of said poles being in directheat exchange with said hardened plastic material on one of said faces,electrical insulating heat conducting means interposed between the otherpole and the other of said faces, said plate having Hall voltageterminals and current supply terminals, leads connected to saidterminals, the leads being in part embedded in said hardened plasticmaterial and in part extended outwardly therefrom.

18. A Hall-efiect electric resistance device of magneticallycontrollable resistance, comprising a resistance plate of magneticallyresponsive substance formed of a semiconducting compound of a carriermobility of at least about 6,000 cm. volt second, said plate havingopposite wide area faces and a thickness of not more than about 0.1 mm.,said plate having Hall voltage terminals and current supply terminals,electric conductor leads connected to said terminals, and a rigidenclosure of hardened electrically insulating material of plastic inwhich said plate and the connected part of the leads are embedded, saidenclosure having two parallel faces to be traversed by magnetic fluxwhen said device is in operation, said enclosure faces extendingparallel to said plate faces on both respective sides thereof and beingnot more than about one mm. thick, said leads and terminals being solocated as to leave free one of the wide area faces of the plate topermit the grinding of the corresponding face of the plastic to reduceits thickness, heat conductive vanes connected to said plastic, and heatconductive powder distributed in said plastic.

19. A Hall generator capable of generating a Hallvoltage power output ofsuch large magnitude as to permit the direct application of the Hallvoltage for the operation of ordinary moving-coil instruments, and fordirect control of electromagnetic relays, magnetic amplifiers, and otherpower consuming devices, comprising a resistance body of magneticallyresponsive substance formed of an A B semiconducting compound of acarrier mobility of at least about 10,000 cm. /volt second, said bodyhaving wide area fiat faces, current supply and Hall voltage electricconductor means joined with said body, and a rigid casting of anelectrically insulating plastic embedding said body and said conductormeans, said conductor means being so located as to leave at least one ofthe flat surfaces of said body unobstructed, pole means for imposingmagnetic flux across said wide area faces, said casting having two facestraversed by the magnetic flux when in operation and extending parallelto said wide area faces on both respective sides thereof and having athickness on said sides of not more than one mm., the said electricallyinsulating ma- 14 terial containing distributed therein an electricallynonconductive heat conductive material to enhance its heat conductance.

20. A Hall eifect resistance apparatus for controlling electric currentflow as a function of magnetic field strength, the apparatusconstituting a generator capable of generating a Hall-voltage poweroutput of such large magnitude as to permit the direct application ofthe Hall voltage for the operation of ordinary moving-coil instruments,and for direct control of electromagnetic relays, magnetic amplifiers,and other power consuming devices, and comprising a plate-shapedsemiconductor member comprised of an A B binary compound having acarrier mobility of at least about 10,000 cmF/volt second, currentsupply and Hall voltage electric conductor means joined with saidmember, and an electrically insulating and supporting structure ofplastic and comprising a first portion within which said conductor meansand all faces of said member are embedded, and which is only slightlygreater in thickness than the thickness of said member, and a secondportion integral with said first portion and of substantially greaterthickness than the thickness of said first portion, said second portioncomprising means for mounting said supporting structure, electricalconnections to said conductor means mounted on said second portion,magnetic pole means juxtaposed in relation to said first portion toimpose magnetic flux across its thickness, heat conductive means atleast partially embedded in said plastic.

21. A Hall effect resistance apparatus for controlling electric currentflow as a function of magnetic field strength, and providing a generatorcapable of generating a Hall-voltage power output of such largemagnitude as to permit the direct application of the Hall voltage forthe operation of ordinary moving-coil instruments, and for directcontrol of electromagnetic relays, magnetic amplifiers, and other powerconsumingdevices, the apparatus comprising a plate-shaped semiconductormember composed of an A B binary compound having a carrier mobility ofat least 10,000 cm. /volt second, current supply and Hall voltageelectric conductor means joined with said member, and a substantiallyrigid, electrically insulating covering of plastic in which saidconductor means and the periphery and at least one planar face of themember are embedded, the covering upon a planar face of saidplate-shaped member being no greater than.

about 1 mm. in thickness, and heat conductive means at least partlyembedded in said plastic.

22. The apparatus of claim 19, the heat conductive material comprising amagnetic ferrite substantially restricted to a part of the plasticbetween the pole means.

References Cited in the file of this patent UNITED STATES PATENTS2,586,609 Burke Feb. 19, 1952 2,594,939 Leete Apr. 29, 1952 2,719,253Willardson et a1. Sept. 27, 1955 2,725,504 Dunlap Nov. 29, 1955 UNITEDSTATES PATENT OFFICE CERTIFICATE or CORRECTION Patent No. 2,915,684December 1 1959 Ottokar .Halla et a1.

It is herebycertified that error appears in the above numbered patentrequiring correction andthat the said .Leteers Patent should read ascorrected below.

I In the grant, line 1, and in the heading to the printed specification,line 5, name of first inventor, for "Ottkar Halla, each occurrence readOttokar Halla Signed and sealed this 21st day of June 1960.

(SEAL) Atfiest:

KARL H. AXLI E ROBERT c. WATSON Attesting Officer I Commissioner ofPatents

